Photorespiration and RuBisCO in C3 Plants — NEET Biology
✅ Asked in NEET 2024(NEET 2024) Given below are two statements: Statement I: In C₃ plants, some O₂ binds to RuBisCO, hence CO₂ fixation is decreased. Statement II: In C₄ plants, mesophyll cells show very little photorespiration while bundle sheath cells do not show photorespiration. In the light of the above statements, choose the correct answer:
(NEET 2024) Given below are two statements: Statement I: In C₃ plants, some O₂ binds to RuBisCO, hence CO₂ fixation is decreased. Statement II: In C₄ plants, mesophyll cells show very little photorespiration while bundle sheath cells do not show photorespiration. In the light of the above statements, choose the correct answer:
The oxygenation activity of RuBisCO enzyme in photorespiration leads to the formation of: (NEET 2020)
Answer & NCERT explanation
Correct answer: C — Statement I is true but Statement II is false
Statement I is correct - in C3 plants, RuBisCO enzyme has dual affinity for both CO2 and O2. When O2 binds to RuBisCO instead of CO2, it leads to photorespiration which reduces CO2 fixation efficiency. Statement II is incorrect - in C4 plants, mesophyll cells do show photorespiration, but bundle sheath cells have very little photorespiration due to high CO2 concentration created by C4 acid decarboxylation.
Read more NCERT concept on the PYQ
In C₃ plants some O₂ does bind to RuBisCO, and hence CO₂ fixation is decreased. Here the RuBP instead of being converted to 2 molecules of PGA binds with O₂ to form one molecule of phosphoglycerate and phosphoglycolate (2 Carbon) in a pathway called photorespiration. In the photorespiratory pathway, there is neither synthesis of sugars, nor of ATP. Rather it results in the release of CO₂ with the utilisation of ATP. In the photorespiratory pathway there is no synthesis of ATP or NADPH. The biological function of photorespiration is not known yet.
NTA tests your understanding of photorespiration—when O₂ binds to RuBisCO instead of CO₂ in C3 plants, reducing carbon fixation. The key trap: students confuse photorespiration with photosynthesis or think it produces ATP and sugars like the Calvin cycle does. Remember, photorespiration consumes ATP and releases CO₂ without producing sugars or ATP—it's essentially wasteful. NEET asks why this happens and its outcomes; the biological function remains unknown, making it a critical concept for C3 vs C4 plant efficiency questions.
What does NCERT say about C plants some O?
Has this concept appeared in NEET?
Which chapter is this from?
Through deep analysis of NEET and NTA, 88 of 90 questions from the NEET 2026 paper were matched straight from the MedicNEET Biology question bank.
88/90MedicNEET's Biology question bank is built from the same NCERT lines NTA picks repeatedly. Not random MCQs — questions crafted exactly like NTA crafts them.